Federal officials need to punish developers of “stalker” applications that track people without their knowledge, Sen. Al Franken (D-Minn.) said on Monday.

Franken, who has been a vocal critic of the apps, is renewing his push against the developers two weeks after the Justice Department made its first arrest of someone trying to sell a spyware app.

“Ending the proliferation and use of these apps is vital to protecting victims of stalking and domestic violence,” he wrote in a letter to Attorney General Eric Holder on Monday.

Franken, the chairman of the Senate Judiciary subcommittee on privacy, has previously pushed Congress to enact new protections for data about people’s location.

“While Congress ultimately must enact such legislation to fully strengthen our federal efforts to protect Americans’ location privacy, there remains more that the [Justice Department] can do under current law to stop those that develop and market stalking apps,” he told Holder.

For instance, the department should go after more app developers, give support to local police and compile new data on the estimated number of victims targeted by stalking apps, Franken proposed.

Last month, a Pakistani man was indicted in Virginia for trying to advertise and sell an app calledStealthGenie, which allowed people to monitor others’ phone conversations, emails and text messages without their knowledge. The arrest was the first of its kind.

“This is a very important and welcome development, and it highlights the danger of stalking apps,” Franken wrote to Holder.

The app industry seemed supportive of Franken’s call.

Jon Potter, the president of the Application Developers Alliance, said in a statement that his trade group “supports enforcement and legislation that targets apps marketed for and intended to facilitate stalking and domestic violence.”

“We look forward to working with Senator Franken and others to accomplish this,” he added.